A resonant reset dual switch forward converter is disclosed. The resonant reset dual switch forward converter includes an input for accepting a dc voltage; a transformer having a primary winding and a secondary winding; a first and a second switch connected in series with the primary winding of the transformer for periodically connecting the input to the primary winding; a resonant capacitor for resetting the transformer during the OFF time of the first and second switches; and an auxiliary switch remaining OFF during the ON time of the first and second switches, and connecting the primary winding to the resonant capacitor during the OFF time of the first and second switches. The resonant reset dual switch forward converter provides a switching duty cycle greater than 50%, obtains a zero-voltage-switching condition for the first and second switches, and maintains the voltage stress of the f first and second switches around the input voltage.
|
1. A resonant reset dual switch forward converter, comprising:
an input for accepting a dc voltage with a low side and a high side; an output; a transformer having a primary winding and a secondary winding; a first and a second switch connected in series with the primary winding of the transformer for periodically connecting the input to the primary winding; a resonant capacitor for resetting the transformer during the OFF time of the first and second switches; a switching device remaining OFF during the ON time of the first and second switches, and connecting the primary winding to the resonant capacitor during the OFF time of the first and second switches; and a rectification circuit connecting the secondary winding to the output.
2. The converter of
3. The converter of
4. The converter of
5. The converter of
6. The converter of
7. The converter of
8. The converter of
9. The converter of
|
1. Field of the Invention
This invention relates generally to the power supply systems that include DC-to-DC conversion operations. More particularly, this invention relates to an improved circuit design and configuration of a forward type DC-to-DC converter with resonant reset.
2. Description of the Prior Art
Forward type topology is widely used in DC-to-DC converters due to the simplicity of the structure. In high input voltage operation, dual switch forward topology is used to reduce the voltage stress of main switches. Due to the limitations of magnetic reset mechanisms, dual switch forward topology is not suitable for wide input voltage operations.
FIG. 1A and
However, since the reset voltage is equal to the input voltage, the reset time is also equal to the turn-on time of the switches in order to keep the voltage-second balance for the transformer. Thus, the maximum switching duty cycle is limited to less than 50% for low input operation conditions. With the increase of the input voltage, the duty cycle becomes small and the performance of the converter deteriorates.
For reducing the conduction loss of the primary side and lowering the voltage stress of the secondary side, it is desirable to increase the duty cycle of the forward converter to greater than 50%. If a resonant reset mechanism is provided in the forward converter, the duty cycle can be designed over than 50% since the reset voltage can be higher than input voltage.
FIG. 2A and
The other disadvantage is that the voltage stress of the switch S1 is the sum of the maximum reset voltage and input voltage, which is about double of input voltage. For these reasons, this topology is only suitable for low input voltage and low power applications.
Therefore, a need still exists to provide a new and improved power converter topology that combines the advantages of dual switch forward and resonant reset forward, but overcomes the disadvantages of the prior art.
It is accordingly an object of the invention to provide a novel and improved resonant reset dual switch forward DC-to-DC converter topology, which overcomes the above-mentioned disadvantages of the prior art. In the preferred embodiment of the present invention, a resonant reset dual forward converter comprises: an input for accepting a DC voltage; a transformer having a primary winding and a secondary winding; two main switches connected in series with the primary winding of the transformer for periodically connecting the input to the primary winding; a resonant capacitor for resetting the transformer during the OFF time of the main switch; an auxiliary switch remaining OFF during the ON time of the main switch, and connecting the primary winding to the resonant capacitor during the OFF time of the main switch; and a rectification circuit connecting the secondary winding to the output.
Due to the large reflected output current, the low side main switch and auxiliary switch turn on under a zero-voltage condition; so a larger resonant capacitor can be used to reset the transformer.
In a further embodiment of this invention, an extra inductor is connected in series with the primary winding or the secondary winding to obtain a zero-voltage-switching condition for the high side switch.
In another embodiment of this invention, a center-tapped S1 rectification circuit is employed. The output inductor can be reduced significantly, and the output voltage ripple is minimized.
In another embodiment of this invention, a current doubler rectification circuit is employed. The output inductor is divided into two smaller ones and the secondary winding need not be tapped. The output voltage ripple is also minimized.
In another embodiment of this invention, a synchronous rectifier circuit is employed to reduce the rectification loss. Meanwhile, a control circuit is needed to maintain the freewheeling rectifier on during the OFF time of main switches.
An advantage of the present invention is that it provides the ability to enlarge the switching duty cycle and reduce the conduction loss of the primary switches.
Another advantage of the present invention is that it obtains a soft switching condition for the main switches. Thus, it provides a converter with high power efficiency.
Another advantage of the present invention is that it requires lower rating voltage switches, so that it can be used for high input voltage conversion design.
For a more complete understanding of the present invention, reference is now made to the following description taken in conjunction with the accompanying drawings, in which:
FIG. 4A and
FIG. 7A and
In the secondary side, a rectifier circuit including rectifiers D1, D2, and a filter circuit including inductor L1 and capacitor C2, which are shown in FIG. 3A. When main switches S1 and S2 turn on, rectifier D1 conducts current from secondary winding to inductor L1 and feeds to load. When main switches S1 and S2 turn off, rectifier D1 is kept off and rectifier D2 conducts the output current.
To illustrate the operation principle of this converter, the operation is divided into two operation modes, the equivalent operation circuits of which are shown in FIG. 4A and FIG. 4B.
A: Forward Mode
When main switches S1 and S2 turn on, the energy in the primary side is forwardly delivered to the secondary side.
B: Resonant Reset Mode
When main switches S1 and S2 turn off, auxiliary switch Sa turns on, and the transformer primary winding is connected with capacitor Cr. By the resonant process of capacitor Cr and magnetizing inductance of the transformer Tr, the transformer Tr is reset.
To illustrate the detailed operation and show the features of this converter, the key waveforms of this converter are shown in FIG. 5. Several time intervals are described as follows:
[1] t0<t<t1
In this time interval, main switches S1 and S2 turn on and auxiliary switch Sa turns off. The drain-to-source voltages of main switches, Vds1 and Vds2, keep zero and the input voltage is applied to the transformer primary winding, so the voltage of transformer is Vin, which keeps the magnetizing current rising linearly. The primary current Ip is the sum of the magnetizing current and reflected output current. The voltage applied to the output filter is the reflected input voltage in secondary side.
[2] t1<t<t2
At time t1 main switches S1 and S2 turn off. After a short dead time, auxiliary switch Sa turns on. The terminal of the primary winding that connects with switch S2 is connected to the low side of the input voltage. The primary current Ip charges the capacitor Cr, the voltage of capacitor Cr increases and the primary current Ip decreases. At t=t2, the energy stored in the leakage inductance of the transformer completely transfers to capacitor Cr. The primary current is equal to the magnetizing current.
[3] t2<t<t3
In this time interval, resonance occurs between capacitor Cr and the magnetizing inductance. The magnetizing current decreases to zero and becomes negative. The voltage of capacitor Cr increases at first, then decreases due to the negative magnetizing current. At time t3, voltage of capacitor Cr drops to zero, and the magnetizing current passes through the body diode of switch S1.
[4]t3<t<t4
In this time interval, the body diode of switch S1 and is auxiliary switch Sa are both are on, the voltage across the primary winding is kept zero, so the magnetizing current keeps constant until the main switches S1 and S2 turn on. At time t4, switch S1 turns on under a zero voltage condition. A new switching cycle begins.
The resonant reset dual switch forward converter of this invention has the following features:
Firstly, since the reset voltage is the resonant voltage of capacitor Cr, it can be made higher than the input voltage by selecting smaller capacitor Cr, so that the reset time can be shorter than switching on time and a switching duty cycle greeter than 50% can be obtained. This not only reduces the RMS current of the primary side but also decreases the voltage stress of rectifiers in secondary side.
Secondly, when main switches S1 and S2 turn off, the drain-to-source voltage of switch S1 is only the reset voltage, and the drain-to-source voltage of switch S2, which is clamped by auxiliary switch Sa, is equal to input voltage. Therefore, the voltage stress of main switches S1 and S2 is about the input voltage instead of double of the input voltage in the single-ended forward converter.
Thirdly, since switch S1 turns on when the voltage of capacitor Cr resonates to zero, no external power loss is generated. Further more, due to the parallel connection of capacitor Cr with switch S1, the turn-off loss of switch S1 is also reduced significantly. Therefore, the switching loss of this converter is much lower.
In a further embodiment of this invention, as shown in
Although the present invention has been described in terms of the presently preferred embodiments, it is to be understood that such disclosure is not to be interpreted as limiting. Various alternations and modifications will no doubt become apparent to those skilled in the art after reading the above disclosure. Accordingly, it is intended that the appended claims be interpreted as covering all alternations and modifications as fall within the true spirit and scope of the invention.
Zhang, Alpha J., Liu, Zhizheng, Huang, Guisong, Gu, Yilei
Patent | Priority | Assignee | Title |
10116202, | Jul 07 2015 | Semiconductor Components Industries, LLC | Adaptive clamping circuitry |
10491129, | Nov 29 2018 | International Business Machines Corporation | Power converter with switchable topology |
10833592, | Nov 29 2018 | International Business Machines Corporation | Power converter with switchable topology |
6888728, | May 25 2001 | TDK Corporation | Switching power supply unit |
7079403, | Dec 09 2002 | QUEEN S UNIVERSITY AT KINGSTON | Isolated DC-DC converters |
7110265, | Dec 09 2002 | GANPOWER INTERNATIONAL INC | Non-isolated DC-DC converters with direct primary to load current |
7307857, | Dec 09 2002 | GANPOWER INTERNATIONAL INC | Non-isolated DC-DC converters with direct primary to load current |
7391629, | Aug 05 2004 | Fairchild Korea Semiconductor, Ltd. | Switching mode power supply with controller for handling overcurrents |
8174852, | Aug 15 2008 | Power Integrations, Inc. | Asymmetric switch forward converter |
8441815, | Aug 15 2008 | Power Integrations, Inc. | Asymmetric switch forward converter |
8625312, | Aug 15 2008 | Power Integrations, Inc. | Asymmetric switch forward converter |
Patent | Priority | Assignee | Title |
4736284, | Jan 14 1986 | Kikusui Electronics Corp. | Switching power supply circuit including forward converter |
5600547, | Dec 21 1994 | Samsung Electro-Mechanics Co., Ltd. | Inverter circuit utilizing a frequency synchronization device |
5822201, | Mar 06 1995 | KIJIMA CO , LTD | Double-ended inverter with boost transformer having output side impedance element |
6141226, | Jun 12 1997 | ABB AB | HVDC transmission system with bidirectionally controlled thyristors |
Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
Apr 18 2001 | HUANG, GUISONG | DELTA ELECTRONICS INC | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 011897 | /0308 | |
Apr 18 2001 | GU, YILEI | DELTA ELECTRONICS INC | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 011897 | /0308 | |
Apr 18 2001 | LIU, ZHIZHENG | DELTA ELECTRONICS INC | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 011897 | /0308 | |
Apr 18 2001 | ZHANG, ALPHA J | DELTA ELECTRONICS INC | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 011897 | /0308 | |
Apr 30 2001 | Delta Electronics Inc. | (assignment on the face of the patent) | / |
Date | Maintenance Fee Events |
Apr 14 2006 | M1551: Payment of Maintenance Fee, 4th Year, Large Entity. |
Apr 14 2010 | M1552: Payment of Maintenance Fee, 8th Year, Large Entity. |
Mar 26 2014 | M1553: Payment of Maintenance Fee, 12th Year, Large Entity. |
Date | Maintenance Schedule |
Oct 22 2005 | 4 years fee payment window open |
Apr 22 2006 | 6 months grace period start (w surcharge) |
Oct 22 2006 | patent expiry (for year 4) |
Oct 22 2008 | 2 years to revive unintentionally abandoned end. (for year 4) |
Oct 22 2009 | 8 years fee payment window open |
Apr 22 2010 | 6 months grace period start (w surcharge) |
Oct 22 2010 | patent expiry (for year 8) |
Oct 22 2012 | 2 years to revive unintentionally abandoned end. (for year 8) |
Oct 22 2013 | 12 years fee payment window open |
Apr 22 2014 | 6 months grace period start (w surcharge) |
Oct 22 2014 | patent expiry (for year 12) |
Oct 22 2016 | 2 years to revive unintentionally abandoned end. (for year 12) |